This invention relates to depth selecting mechanisms and more particularly to a sonobuoy depth selector which permits a selectable predetermined length of line to be paid out from a suspended underwater sonobuoy to a supporting float.
Of the various prior art devices which have been used for suspending or tethering an object at a predetermined distance below the surface of the water or above the ocean bed, a squib operated selector mechanism has been found to be among the most reliable. In operation, the sonobuoy containing a coil of signal cable deploys a float to which one end of the cable is attached. The sonobuoy descends while paying out cable from the cable coil until the shallow operating depth is reached. At this point, an arresting loop attached to the cable and also to the sonobuoy bulkhead is pulled taut and stops the descent of the sonobuoy. The loop passes through a cable cutter which is in turn attached to the sonobuoy bulkhead. Upon receiving a signal from the transceiver contained within the float, the squib fires pushing a piston type cutter which severs the loop. Severing of the loop allows the sonobuoy to descend paying out the remainder of the signal cable coil until a loop connected to the cable near the end of the cable coil is pulled taut. The latter loop is simply wrapped around the body of the cable cutter.
To incorporate a third depth capability utilizing the above technique would require a second cable cutter, which would be difficult to package, along with another bulkhead penetration for the squib electrical lead, which lowers the reliability of water tight integrity. Accordingly, there exists a need for a device which selects more than two depth line lengths at which the sonobuoy may float while providing convenient, reliable operation and which is inexpensive.